John Sayer, 49, from Canary Scaffolding, on Ace industrial estate, Stratton Strawless, near Norwich, was also found with five knuckle-dusters, two extendable batons and another stun gun, when his luggage was searched after a trip to Thailand, where his wife is from, on May 21 last year.

Sayer, who had denied possessing the prohibited weapons and claimed it was a “total mistake” they were in his luggage was yesterday found guilty at Norwich Crown Court.

The jury of seven women and five men took just two hours and 50 minutes to find Sayer guilty of three offences - possession of a disguised firearm, having an offensive weapon and possession of a prohibited weapon - and was remanded in custody.

Judge Peter Jacobs, who adjourned sentence until Monday, warned that the offences carry a mandatory five year prison term.

During the trial, which started on Monday, the court heard that Sayer had in 2010 been prosecuted after police discovered prohibited weapons - including three stun guns and CS spray - at his home after he brought them back for his wife although he said he was not then aware they were illegal.

But Sayer, who subsequently had his firearms licence taken away, said the items found last May were not meant to be in his suitcase but were part of “stock” from stalls owned by his wife’s late grandfather which were not meant to be in his luggage.